1. Field of the Invention
The present invention relates to an automobile body frame which is formed of a light metal such as aluminum alloy.
The present application is based on Japanese Patent Applications No. Hei. 10-37200 and No. Hei. 10-312855, which are incorporated herein by reference.
2. Description of the Related Art
An automobile body frame of a space frame type comprising welded hollow members in structure is generally such that front side frames are extendedly provided on the respective inner sides of front wheels; side sills are extendedly provided on the respective side ends of a passenger room flooring; and the rear sides of the front side frames and the front ends of the side sills are all connected to a dash board lower cross member. According to this type, the coupling ends at which the front side frame and the side sill are coupled to the dash board lower cross member are respectively set in offset positions in the width direction of an automobile. As a result, when the automobile undergoes a head-on collision, an input position where the crashing load applied from the front side frame and an input position where the counterforce load applied from the side sill are input to the dash board lower cross member are shifted from each other. Accordingly, a coupling portion where each front side frame and the dash board lower cross member are coupled together tends to easily bend toward the inside of the passenger room.
It is undesirable to cause the deformation of the automobile body to develop into the passenger room, so the rigidity of the passenger room flooring has been increased by enlarging the sectional areas of the dash board lower cross member and the side sills. However, if the sizes of the dash board lower cross member and the side sill are increased, comfortableness in the passenger room and boarding-alighting ease deteriorate.
Further, there is another problem in the case of a side impact. In order to protect a passenger from the side impact, a center pillar must be restrained from developing into a passenger room. Consequently, the bending rigidity of the coupling portion between the center pillar and a side sill should be increased. Hence, a relatively greater sectional area is normally secured for the side sill, which may result in sacrificing the boarding-alighting ease.